Thousands of demonstrators protest against the planned Transatlantic Trade and Investment Partnership in Hannover (AP)

Two women carry signs against the TTIP free trade agreement during a protest march against the upcoming G7 summit on June 4, 2015 in Munich, Germany. The leaders of the G7 nations are scheduled to meet at nearby Schloss Elmau June 7-8. (Photo by Sean Gallup/Getty Images)

MUNICH, GERMANY - JUNE 04: People demonstrating against the upcoming G7 summit carrier a banner that decries the TTIP free trade agreement during a protest march on June 4, 2015 in Munich, Germany. The leaders of the G7 nations are scheduled to meet at nearby Schloss Elmau June 7-8. (Photo by Sean Gallup/Getty Images)

MUNICH, GERMANY - JUNE 04: People wearing signs against the TTIP free trade agreement take a break during a protest march against the upcoming G7 summit on June 4, 2015 in Munich, Germany. The leaders of the G7 nations are scheduled to meet at nearby Schloss Elmau June 7-8. (Photo by Sean Gallup/Getty Images)

Protesters against the trade deal marching in London

The UK Parliament may not have the power to stop or reverse the privatisation of the NHS if the Transatlantic Trade and Investment Partnership passed at EU level, Unite has warned.

The union cites a letter from Lord Maude of Horsham, the minister for trade and investment, in response to a query from a constituent of Labour MP Jim Fitzpatrick about how TTIP would pass into law in the UK.

In the letter, Lord Maude of Horsham says that the UK Parliament could delay the ratification of the final text of TTIP “indefinitely” by repeatedly voting against it in the House of Commons and the Lords.

Gail Cartmail, Unite assistant general secretary, said that it was “a scandal” that MPs may not have the democratic power to stop TTIP, which she said “threatens the irreversible sell-off of our NHS”.

“The House of Commons will have the power to delay the trade deal but it would only be a matter of time before TTIP eventually slips through,” Ms Cartmail said.

A spokeswoman for the Department for Business, Innovation and Skills said that under EU law, treaties of this kind are subject to approval by each individual EU member state before coming into force.

“All such agreements are subject to Parliamentary scrutiny before they are finalised,” the spokeswoman said.

But similar agreements such as the EU-Korea free trade agreement have shown that trade agreements can be “provisionally applied” before being ratified by national parliaments.

Obama's trip to Europe has been seen as an effort to drum up support for TTIP before the end of his time in the White House AFP/Getty Images

“A lot is still up in the air right now and will depend on how the competence battles between the Commission and the Member States play out. But there is of course the possibility that the agreement was provisionally applied in parts before Member State parliaments had their say on it,” said Gabriel Siles-Brügge, a politics lecturer at the University of Manchester who has written a book on TTIP.

Tamara Hervey, a professor of EU law at the University of Sheffield, said that it was legally debateable what kind of process the UK Government would go through to pass TTIP in the UK and whether opposition in parliament would delay it “indefinitely”.

Either way, it would be possible to protect the NHS by excluding it from TTIP negotiations altogether – something that the UK Government has so far declined to do.

TTIP: the proposed free trade treaty could become the biggest such deal ever made

“The UK government could include a reservation in the agreement to say that it does not include the NHS. As far as I understand, that isn't on the table, even though several other EU countries have already put such reservations in the negotiating text,” Professor Hervey told the Independent.

Opponents claim TTIP would lead to public services including health being privatised, but backers insist it would boost jobs and business

Austria, Germany, Greece and Italy do have explicit reservations in the TTIP text to protect existing rules relating to healthcare. But the UK hasn’t entered any reservations in this part of the TTIP text, Professor Hervey said.

“Cyprus seems more worried about US hairdressers than the UK is about this. It has a reservation for hairdressing services,” she notes in a recent blog post on the issue.

A series of polls commission by the campaign group 38 Degrees has shown that Scottish voters are more opposed to TTIP than those in the UK. A poll of more than 2,000 Scots revealed that 70 per cent of Scottish voters oppose the inclusion of the NHS in the TTIP agreement. A similar poll conducted in the UK found that 44 per cent were opposed.